1) Field of the Invention
The present invention relates to a cartridge transferring robot for use in a library apparatus which stores a large number of cartridges such as magnetic tape cartridges and optical disk cartridges, with the cartridge transferring robot conveying of the cartridges among a storage rack, a cartridge entry/exit station and a deck unit within the library apparatus, and further relates to a library apparatus including that cartridge transferring robot.
2) Description of the Related Art
In general, a library apparatus functions as a large-capacity external storage memory, and a storage rack in its locker stores several thousands of cartridges each accommodating, for example, a magnetic tape as a storage medium, and access such as write/read of recording/recorded data is automatically done in relation to the storage medium within each of the cartridges.
Furthermore, in addition to the aforesaid storage rack (storage unit) for storing the cartridges, the library apparatus is equipped with a station [for example, a CAS (Cartridge Access Station), a DEE (Direct Entry/Exit), and an FES (Forced Exit Station)] for carrying out the entry of the cartridges from the external into the apparatus or vice versa, a plurality of magnetic tape decks (which will be referred hereinafter to as decks) for conducting access such as write/read of recording/recorded data with respect to a storage medium (magnetic tape) within a cartridge, and a cartridge transferring robot [automatic transferring robot; which will be referred hereinafter to as an accessor (ACC)] for performing the conveyance of the cartridges among the storage rack, the cartridge entry/exit station and the decks.
In the case of such a library apparatus, on receiving an access demand to one cartridge from a host unit or the like, the accessor moves to the storage rack to search the directing cartridge and then transfers that cartridge up to the deck in a state of gripping or holding it through the use of a hand mechanism, thereby putting it into that deck. Whereupon, the deck processes the storage medium (magnetic tape) within the cartridge. The cartridge discharged from the deck after the completion of the processing is regripped by the hand mechanism of the accessor and transferred up to the storage rack by that accessor to be stored in a given location.
In the prior art, the hand mechanism of the accessor is constructed, for example, as shown in FIGS. 7 and 8. That is, the hand mechanism has a pair of upper and lower hand members 100a, 100b for gripping a cartridge (not shown) by coming into contact with the cartridge from the above and below, and these hand members 100a, 100b are attached through a direct-acting (or direct-operated) bearing (LM guide) 110 to a hand base (not shown) to be slidable up and down. Between the hand members 100a, 100b there are interposed a plurality of (3 in FIG. 7) springs 120 whereby the hand members 100a, 100b are biased in closing directions of gripping a cartridge.
The direct-acting bearing 110 is composed of one guide rail 111 fitted to the hand base side and two blocks (bearings) 112a, 112b guided along the guide rail 111 to be slidable up and down, with the hand members 100a, 100b being attached to these blocks 112a, 112b, respectively.
Furthermore, rods 130a, 130b are protrusively installed on rear end surfaces of the hand members 100a, 100b, respectively. The hand members 100a, 100b are respectively connected through the rods 130a, 130b to an opening and closing mechanism (not shown) so that the hand members 100a, 100b are vertically driven against the biasing forces of the springs 120 to take the opening and closing action.
In the case of this hand mechanism, its thickness depends upon the length of the guide rail 111 constituting the direct-acting bearing 110. As shown in FIG. 7 or 8, in the structure including only one direct-acting bearing 110, the respective blocks 112a, 112b increase in size because of the loads on the blocks 112a, 112b, with the result that the guide rail 111 becomes longer, that is, the hand mechanism has a larger thickness.
For this reason, a prior hand mechanism shown in FIG. 9 has been proposed. In FIG. 9, the hand mechanism uses two direct-acting bearings 110, so that the size reduction of the blocks 112a, 112b to be respectively guided along the direct-acting bearings 110, 110 is achievable, which contributes to shorter lengths of the guide rails 111. Though, when the two direct-acting bearings 110, 110 are used in parallel to each other, the fitting surfaces of the two guide rails 111 are required to have extremely high parallelism and flatness, and if not, the sliding resistance of the respective blocks 112a, 112b sliding along the guide rails 111 increase.
On the other hand, in the prior accessor hand mechanism, as shown in FIGS. 7 to 9, the surfaces (gripping portions) of the hand members 100a, 100b coming into contact with a cartridge to grip that cartridge are large in area, and therefore, there is no need for a particularly strong gripping force being applied through the hand members 100a, 100b to a cartridge. Whereas, in connection with the tendency toward the reduction of the hand mechanism of the accessor in size and weight, the areas of the aforesaid gripping portions also reduce. Accordingly, at the conveyance or insertion/extraction of a cartridge, it is necessary to apply a strong gripping force to a cartridge in order to certainly grip the cartridge by the hand mechanism.
For such a strong gripping force, consideration can be paid to ways to increase the number of springs 120 to be put between the hand members 100a, 100b and to select springs 120 having stronger forces. However, in the case of increasing the number of springs 120, there is a need for a further space accepting the increased springs 120, which makes the size reduction of the hand mechanism difficult.
Furthermore, even if employing stronger springs, the opening degree between the hand members 100a, 100b decreases with respect to the thickness of the hand mechanism, with the result that not only difficulty is encountered in that the springs themselves assume a long free length but also a restriction occurs in that the springs are required to exhibit a stronger force with less distortion, which adversely affects the degree of freedom on the spring design, and which makes difficult the appropriate design depending on the dimensional conditions.
In conjunction with the recent increase in the volume of information in computer systems, as a means to retain information in a state of freely making the recording/reproduction without the need for an operator, the library apparatus fully automatized as mentioned above appears, which allows storing a large number of cartridges. On the other hand, for the future, it is desired to store a larger number of cartridges in a limited installation space. In order to enhance the cartridge storing efficiency, it is indispensable to dispose cells in a storage rack with a higher density.
For the insertion/extraction of cartridges into/from such cells disposed with a high density, it is essential to enlarge the operating range of a hand mechanism of an accessor, and further to accomplish the reduction of the hand mechanism itself in size, weight and thickness. In addition, it is desired to certainly grip the cartridges irrespective of the size reduction of the hand mechanism.